It has been proposed to improve the biocompatibility of metal prostheses such as a titanium prosthesis by modifying the metal surfaces thereof, e.g. by plasma bombardment, etching or electrolysis.
Anodic oxidation has been described for the formation of a thick oxide layer (i.e. thicker than the naturally occurring oxide layer) on an implant surface. For instance, WO 00/72777 describes an electrolytic oxidation process wherein an implant is immersed in an acidic electrolyte and the implant (anode) is brought into contact with an electric energy source connected to a counter-electrode (cathode) immersed in the same acidic electrolyte.
It has also been proposed to improve the biocompatibility of prostheses and implants by binding or integrating various active biomolecules to the surface of the prosthesis, e.g. on to the metallic surface of a titanium prosthesis. It has been the aim with implants prepared this way that they have improved fit; exhibit increased tissue stickiness and increased tissue compatibility; have a biologically active surface for increased cell growth, differentiation and maturation; exhibit reduced immunoreactivity; exhibit antimicrobial activity; exhibit increased biomineralization capabilities; result in improved wound and/or bone healing; lead to improved bone density; have reduced “time to load” and cause less inflammation.
Such binding has often been carried out using for example chemical reactants having two reactive functionalities such as formalin or glutaraldehyde, but the reactive nature of these agents often leads to the biomolecules becoming biologically inactive and/or with enhanced immunoreactivity which is undesirable.